Many products, including consumer and professional products, are more effectively used by an end user when they include a feature that indicates a particular condition or degree of use. An example of a visual indicator is a color indicator. Color indicators can either indicate a change in condition or a degree of use through a change from “color” to “no color” (or vice versa) or through a change from one color to a different color.
Exemplary conditions that could be monitored using a color indicator include physical conditions such as the presence of moisture and chemical conditions. Exemplary consumer products that could be more effective and deliver more benefits to end users by incorporating a suitable color indicator include absorbent articles, facial tissues, bath tissue, paper towels, household cleaning items and personal cleaning wipes. Exemplary professional products that could be more effective and deliver more benefits to end users by incorporating a suitable color indicator include products for medical use, safety garments, industrial cleaning products and nonwoven materials.
Color indicators are well known and are available in various forms. Desirable performance attributes include durability and good retention (i.e. the color indicator remains where intended and does not leach out into other components of the product within which it is being used). Depending on the product application, it may also be desirable to have the structure in which the color indicator is used be wettable, but water-insoluble. It may also be desirable for the color indicator to have a distinct, or sharp, color change and a rapid response time to aid the user in identifying the physical condition change in the product. For purposes of applying the color indicator to a component of a product, it may also be desirable to have a color indicator that can be applied in liquid form at room temperature (American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE) standard range of 20° C. to 25° C. at 40% to 60% relative humidity). When the color indicator is in a liquid form at room temperature, the color indicator can be easily printed (just like an ink composition) onto the desired component of a product.
Examples of how color indicators are already incorporated into consumer products include diapers that have wetness sensors. Some of the wetness sensors used in diapers lose color to indicate wetness while others develop color in response to wetness (i.e. the color appears when the indicator is dissolved by water). The concept of incorporating a color-changing composition into a wearable article (such as a disposable diaper) is known in the art. For example, U.S. Patent Application Publication No. 2010/0030173 by Song et al. (hereinafter “the '173 publication”) is directed to a wetness sensor for an absorbent article. The color-changing composition of the '173 publication includes an electron-donating leuco dye and an electron deficient receptor. The wetness-indicating composition may include surfactants. The surfactants may be non-ionic surfactants, ionic surfactants or a mixture thereof. The wetness-indicating composition of the '173 publication transitions from a color, to a weaker color and perhaps will become colorless in response to water-containing liquids. The wetness-indicating composition of the '173 publication can fade color with prolonged exposure and increased amounts of a water-containing liquid. The strong color of the indicating materials begins to fade in proportion to the amount and contact time with a water-containing liquid (i.e. the composition is able to indicate different degrees or levels of wetness over time). While the wetness-indicating compositions of the '173 publication are capable of becoming colorless, the compositions do not provide rapid and distinct color change after exposure to water-containing liquids. The surfactant of the '173 publication composition is not necessary to invoke the disappearance of color.
Another example of color-changing compositions known in the art is ink used with writing instruments. It is sometimes desirable to remove ink that has been accidentally written on paper, walls or furniture. For example, U.S. Pat. No. 5,417,748 by Kawashima (hereinafter “the '478 patent”) is directed to a writing instrument that contains a color ink agent. The color ink agent of the '478 patent consists of certain electron donative coloring compounds and certain electron acceptive developing compounds. The color ink agent of the '478 patent changes from a state of color to a state of becoming colorless in response to water-containing liquids. The color ink agent of the '478 patent is intended for convenient and clean erasure of the ink from a surface. The color ink agent of the '478 patent doesn't require the need to maintain the ink on a preprinted surface until it is desired for the composition to change color. The color ink agent of the '478 patent also does not require the need for rapid and distinct color change. As a result, the '478 patent does not address the need for additional components in the color ink agent beyond electron donative coloring compounds and electron acceptive developing compounds.
While the color-changing compositions known in the art provide certain benefits, there remains a need for a composition that shows rapid and distinct, or acute, color change for ease of reading when the composition is used in a product. There also remains a need for the composition to be durable and remain where intended in the product. When the purpose of the composition is to detect the presence of wetness, there remains a need for a composition that is water-resistant and water-insoluble. There remains a need for a composition that can be printed on a substrate. Further, there remains a need for a composition that can be applied, such as by printing, at room temperature so that the composition can be applied to a substrate without heating. In addition to the needs identified above, there are unmet needs associated with using multi-component materials as components of personal care absorbent articles, such as disposable diapers. In particular, there is a need for a color-changing composition that maintains its efficacy when used in conjunction with outer cover material.